Unity Linux 20.1070e Security Update: kernel (UTSA-2025-989839)

high Nessus Plugin ID 273359

Synopsis

The Unity Linux host is missing one or more security updates.

Description

The Unity Linux 20 host has a package installed that is affected by a vulnerability as referenced in the UTSA-2025-989839 advisory.

In the Linux kernel, the following vulnerability has been resolved:

tcp_bpf: Fix the sk_mem_uncharge logic in tcp_bpf_sendmsg

The current sk memory accounting logic in __SK_REDIRECT is pre-uncharging tosend bytes, which is either msg->sg.size or a smaller value apply_bytes.

Potential problems with this strategy are as follows:

- If the actual sent bytes are smaller than tosend, we need to charge some bytes back, as in line 487, which is okay but seems not clean.

- When tosend is set to apply_bytes, as in line 417, and (ret < 0), we may miss uncharging (msg->sg.size - apply_bytes) bytes.

[...] 415 tosend = msg->sg.size;
416 if (psock->apply_bytes && psock->apply_bytes < tosend) 417 tosend = psock->apply_bytes;
[...] 443 sk_msg_return(sk, msg, tosend);
444 release_sock(sk);
446 origsize = msg->sg.size;
447 ret = tcp_bpf_sendmsg_redir(sk_redir, redir_ingress, 448 msg, tosend, flags);
449 sent = origsize - msg->sg.size;
[...] 454 lock_sock(sk);
455 if (unlikely(ret < 0)) { 456 int free = sk_msg_free_nocharge(sk, msg);
458 if (!cork) 459 *copied -= free;
460 } [...] 487 if (eval == __SK_REDIRECT) 488 sk_mem_charge(sk, tosend - sent);
[...]

When running the selftest test_txmsg_redir_wait_sndmem with txmsg_apply, the following warning will be reported:

------------[ cut here ]------------ WARNING: CPU: 6 PID: 57 at net/ipv4/af_inet.c:156 inet_sock_destruct+0x190/0x1a0 Modules linked in:
CPU: 6 UID: 0 PID: 57 Comm: kworker/6:0 Not tainted 6.12.0-rc1.bm.1-amd64+ #43 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014 Workqueue: events sk_psock_destroy RIP: 0010:inet_sock_destruct+0x190/0x1a0 RSP: 0018:ffffad0a8021fe08 EFLAGS: 00010206 RAX: 0000000000000011 RBX: ffff9aab4475b900 RCX: ffff9aab481a0800 RDX: 0000000000000303 RSI: 0000000000000011 RDI: ffff9aab4475b900 RBP: ffff9aab4475b990 R08: 0000000000000000 R09: ffff9aab40050ec0 R10: 0000000000000000 R11: ffff9aae6fdb1d01 R12: ffff9aab49c60400 R13: ffff9aab49c60598 R14: ffff9aab49c60598 R15: dead000000000100 FS: 0000000000000000(0000) GS:ffff9aae6fd80000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007ffec7e47bd8 CR3: 00000001a1a1c004 CR4: 0000000000770ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 PKRU: 55555554 Call Trace:
<TASK> ? __warn+0x89/0x130 ? inet_sock_destruct+0x190/0x1a0 ? report_bug+0xfc/0x1e0 ? handle_bug+0x5c/0xa0 ? exc_invalid_op+0x17/0x70 ? asm_exc_invalid_op+0x1a/0x20 ? inet_sock_destruct+0x190/0x1a0
__sk_destruct+0x25/0x220 sk_psock_destroy+0x2b2/0x310 process_scheduled_works+0xa3/0x3e0 worker_thread+0x117/0x240 ? __pfx_worker_thread+0x10/0x10 kthread+0xcf/0x100 ? __pfx_kthread+0x10/0x10 ret_from_fork+0x31/0x40 ? __pfx_kthread+0x10/0x10 ret_from_fork_asm+0x1a/0x30 </TASK>
---[ end trace 0000000000000000 ]---

In __SK_REDIRECT, a more concise way is delaying the uncharging after sent bytes are finalized, and uncharge this value. When (ret < 0), we shall invoke sk_msg_free.

Same thing happens in case __SK_DROP, when tosend is set to apply_bytes, we may miss uncharging (msg->sg.size - apply_bytes) bytes. The same warning will be reported in selftest.

[...] 468 case __SK_DROP:
469 default:
470 sk_msg_free_partial(sk, msg, tosend);
471 sk_msg_apply_bytes(psock, tosend);
472 *copied -= (tosend + delta);
473 return -EACCES;
[...]

So instead of sk_msg_free_partial we can do sk_msg_free here.

Tenable has extracted the preceding description block directly from the Unity Linux security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

Solution

Update the affected kernel package.

Plugin Details

Severity: High

ID: 273359

File Name: unity_linux_UTSA-2025-989839.nasl

Version: 1.1

Type: local

Family: Unity Linux Local Security Checks

Published: 11/5/2025

Updated: 11/5/2025

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 6.7

CVSS v2

Risk Factor: Medium

Base Score: 6.8

Temporal Score: 5

Vector: CVSS2#AV:L/AC:L/Au:S/C:C/I:C/A:C

CVSS Score Source: CVE-2024-56633

CVSS v3

Risk Factor: High

Base Score: 7.8

Temporal Score: 6.8

Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

Required KB Items: Host/local_checks_enabled, Host/cpu, Host/UOS-Server/release, Host/UOS-Server/rpm-list

Exploit Ease: No known exploits are available

Patch Publication Date: 11/5/2025

Vulnerability Publication Date: 12/27/2024

Reference Information

CVE: CVE-2024-56633

Detections

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